1. Field of the Invention
The present invention relates to archery bows, and more particularly to archery bows having a draw pull let-off feature. Still more particularly, the present invention pertains to an archery apparatus for propelling an arrow characterized by a rigid main frame, wherein the bowstring thereof, when drawn, is tensioned by one or more resilient members in conjunction with actuation of a cam and pulley assembly.
2. Description of the Prior Art
Simple archery bows are composed of a bow member (or back) characterized by a handle having connected thereto on each side thereof a flexibly resilient limb, and a bowstring connected with opposite ends of the bow member. The archer places the nock of an arrow against the nocking point of the bowstring and then draws the bowstring, thereby causing the bow member to resiliently flex at the limbs. This flexing of the bow member supplies tension to the bowstring and stores potential energy (draw energy). When the bowstring is released, the tension of the bowstring applies a force to the arrow, whereupon the potential energy of the bow member is captured by the arrow in the form of kinetic energy. While such an archery bow has the advantage of being simply constructed, it suffers from the need of the archer to continuously supply draw pull to keep the bow member resiliently flexed. Another serious disadvantage is the essentially instantaneous application of bowstring force upon the arrow at the moment the bowstring is released, with consequent degredation of accuracy due to the imparted shock. An improved example of a simple archery bow using springs to reduce bowstring shock is described in U.S. Pat. No. 4,570,606 to Peck.
These problems have been addressed in the past with varying degrees of success, wherein it is an object to provide an archery bow having a draw pull let-off feature, while yet providing a high level of draw energy for imparting ample speed to the arrow when released.
In this regard, compound archery bows have been devised toward addressing these objects, generally utilizing a rigging of the bowstring with respect to one or more cams or pulleys which are rotatively mounted with respect to the bow member. As the bowstring is pulled back, the limbs of the bow member are caused to resiliently flex, while rotation of the cams or pulleys as the bowstring is pulled back causes the force on the bowstring to be high during pull back of the bowstring and then let-off as the maximum draw point is achieved. Examples of such compound bows are described in U.S. Pat. Nos. 4,718,397 to Remick, 4,461,267 to Simonds et al, 4,562,824 to Jennings, and 4,519,374 to Miller. Imaginative and interesting variations on this principle are found in U.S. Pat. Nos. 5,045,463 to Colley et al, 4,817,580 to Butterfield, 3,851,638 to Alexander, and 2,714,377 to Mulkey.
While compound archery bows such as those indicated hereinabove do address the objects of providing draw energy and a draw pull let-off, they suffer from one or more of the following detractions: complexity; adjustment difficulty; handling difficulty occasioned by at least one of excessive weight, bulk and/or high center of gravity; undue friction of the bowstring caused by excessively intricate rigging, inability to provide a completely adjustable draw pull let-off; and reliance on resilient flexing of the bow member to provide tension on the bowstring which reliance may limit the draw energy and may reduce accuracy due to vibration associated with bow member movement.
Accordingly, it would be desirable to provide an archery apparatus which provides a completely adjustable draw pull let-off, yet provides a high level of draw energy, and further which is not overly complex, is not cumbersome, is easily adjustable and which does not rely upon resilient flexing of the bow member to provide tensioning of the bowstring.